Abstract-Terahertz imaging sensor based on the strong coupling of surface plasmon polaritons between PVDF and graphene

Jiaqi Zhu, Banxian Ruan, Qi You, Jun Guo,  Xiaoyu Dai, Yuanjiang Xiang

https://www.sciencedirect.com/science/article/pii/S0925400518304696
Surface plasmon polaritons (SPPs) of metal materials such as gold and silver are excited in the visible and near-infrared band, while the graphene SPPs exist from mid-infrared to terahertz (THz) ranges. Hence it is difficult to realize the coupling of SPPs of metals and graphene. In this paper, we realize coupling of two SPPs modes based on graphene and polyvinylidene fluoride (PVDF) in THz range, which is vital for the research of new sensors in terahertz spectrum. Based on the dispersion relation, it is demonstrated that the two different THz SPP modes in the hybrid configuration can be coupled together. We apply our design to the imaging sensor, and the highest imaging sensitivity as high as 730RIU⁻¹ is realized in the proposed sensors (which can be used in gas detection). Our results suggest that the strong coupling of two SPPs modes is an efficient method to achieve high sensing properties for the devices.

Abstract-Highly Sensitive Terahertz Gas Sensor Based on Surface Plasmon Resonance With Graphene

Yuanjiang Xiang,   Jiaqi Zhu, Leiming Wu,  Qi You,  Banxian Ruan, Xiaoyu Da

One of the most important applications of THz frequencies is biomedical sensing. However, in a THz range, surface plasmon waves on flat metals are not confined and therefore cannot be used for subwavelength sensing. But, it has been shown that graphene can support surface waves at THz frequencies, which has similar properties as plasmonic waves in an optical range. In this paper, a highly sensitive gas sensor in the terahertz frequencies by exciting surface plasmon resonance (SPR) of graphene is proposed. The results show that the proposed SPR gas sensor has high stability and high sensitivity (S), and the highest Smax (∼147°/RIU) has been obtained by optimizing the Fermi energy, the thickness of the dielectric layer, and the incident light frequency. Moreover, the S of the proposed THz sensor for different refractive index (RI) of gas sensing medium (n1) is also discussed.

Abstract-Tunable and multichannel terahertz perfect absorber due to Tamm surface plasmons with graphene

Xi Wang, Xing Jiang, Qi You, Jun Guo, Xiaoyu Dai, and Yuanjiang Xiang

https://www.osapublishing.org/prj/abstract.cfm?uri=prj-5-6-536

In this paper, we have shown that perfect absorption at terahertz frequencies can be achieved by using a composite structure where graphene is coated on one-dimensional photonic crystal (1DPC) separated by a dielectric. Due to the excitation of optical Tamm states (OTSs) at the interface between the graphene and 1DPC, a strong absorption phenomenon occurs induced by the coupling of the incident light and OTSs. Although the perfect absorption produced by a metal–distributed Bragg reflector structure has been researched extensively, it is generally at a fixed frequency and not tunable. Here, we show that the perfect absorption at terahertz frequency not only can be tuned to different frequencies but also exhibits a high absorption over a wide angle range. In addition, the absorption of the proposed structure is insensitive to the polarization, and multichannel absorption can be realized by controlling the thickness of the top layer.

© 2017 Chinese Laser Press

Abstract-Ultrasensitive Terahertz Biosensors Based on Fano Resonance of a Graphene/Waveguide Hybrid Structure

Banxian Ruan, Jun Guo, Leiming Wu, Jiaqi Zhu, Qi You, Xiaoyu Dai, Yuanjiang Xiang,

http://www.mdpi.com/1424-8220/17/8/1924

Graphene terahertz (THz) surface plasmons provide hope for developing functional devices in the THz frequency. By coupling graphene surface plasmon polaritons (SPPs) and a planar waveguide (PWG) mode, Fano resonances are demonstrated to realize an ultrasensitive terahertz biosensor. By analyzing the dispersion relation of graphene SPPs and PWG, the tunable Fano resonances in the terahertz frequency are discussed. It is found that the asymmetric lineshape of Fano resonances can be manipulated by changing the Fermi level of graphene, and the influence of the thickness of coupling layer and air layer in sandwich structure on the Fano resonances is also discussed in detail. We then apply the proposed Fano resonance to realize the ultrasensitive terahertz biosensors, it is shown that the highest sensitivities of 3260 RIU−1 are realized. Our result is two orders of a conventional surface plasmon resonance sensor. Furthermore, we find that when sensing medium is in the vicinity of water in THz, the sensitivity increases with increasing refractive index of the sensing medium.